Description of the
flag

The provincial flag, as seen during the 2016
inauguration of the President of Gabon, is white with the provincial
coat-of-arms occupying 4/5 of the height in the centre.

According to Heraldry of
the World, the gold colour stands for the richness of the mines in the
district, the mask for traditional art and crafts. The chief recalls the colour
of coffee which is produced here. The lozenges represents the diamond mining in
the district, their number stands for the districts of the region (so probably
before 1975 administrative reform).Olivier Touzeau, 29 Dec 2016

So the coat of arms of Ngounié was modified in 1975
following territorial reform : it then had seven departments. Between 1996
and 2000, to more departments were created (according to
http://www.statoids.com/yga.html.
Louetsi-Bibaka department split from Boumi-Louetsi and Mougalaba department
split from Douya-Onoye, but the chief of the arms was not modified to 9 lozenges
and remains at 7.Olivier Touzeau, 29 Dec 2016